The present invention relates to an equipment for precalcining any mineral materials whatsoever such for example as cement clinker, lime, alumina, magnesia or dolomite.
It is also directed to a method of precalcining such materials.
There has already been proposed equipment for precalcining mineral materials comprising in particular a precalciner essentially consisting of a combustion chamber fed with hot air, of a reaction chamber communicating with the combustion chamber and supplied with smokes rich in nitrogen oxides issuing from a firing or calcining furnace, oven or like kiln and of a cyclone permitting the separation of the material and connected to the reaction chamber by a duct.
It is possible to operate this kind of equipment during a reducing run so as to at least partially remove the nitrogen oxides. The reduction of the nitrogen oxides however is limited because in such equipments is generated during a reducing run much unburnt carbon which is practically inactive for the reduction of the nitrogen oxides. Moreover this unburnt carbon is difficult to be subsequently reoxidized and is detrimental to the good operation of the firing furnace.